1. Field of the Invention
The present invention relates to a plasma CVD method of using a plasma CVD apparatus. More particularly, the present invention relates to a plasma CVD apparatus in which a plasma generation region and a substrate processing region are separated and which is suitable for a large area CVD film formation.
2. Description of the Related Art
As one of the plasma CVD apparatuses for forming a film on a substrate while restraining plasma damage, a remote-plasma CVD apparatus is known in which a plasma generation region and a substrate processing region are separated. A method of forming a CVD film using such a remote-plasma CVD apparatus is an important technology as the processing process to make a highly reliable device and a highly efficient device in a semiconductor device process. The remote plasma CVD apparatuses can attain the large sized substrate processes such as a large area flat panel display switching transistor forming process, a drive circuit transistor forming process and a large diameter silicon wafer process. As such a remote plasma CVD apparatus, a parallel plate remote plasma CVD apparatus is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 5-21393). As shown in FIG. 1, the parallel plate remote plasma CVD apparatus is composed of a high frequency applied electrode 101 and a counter electrode 102 on which a substrate 103 is mounted. A plasma confining electrode 108 as a mesh plate having a plurality of holes is provided between the high frequency applied electrode 101 and the counter electrode 102. Plasma 106 is confined between the high frequency applied electrode 101 and the plasma confining electrode 108. Plasma generation gases 111 are introduced between the high frequency applied electrode 101 and the plasma confining electrode 108. The vacuum chamber 107 is provided with an exhaust port 116.
Such a parallel plate remote plasma CVD apparatus using the plasma generated between parallel plates can uniformly supply radicals necessary to process a substrate in a large area. The apparatus disclosed in the above mentioned Japanese Laid Open Patent Application (JP-A-Heisei 5-21393) is provided with neutral gas injection holes 109 near the passage holes 105 for the radicals 104. The large area uniform process is possible through the reaction of the radicals 104 and the neutral gas 110. For this reason, the parallel plate remote plasma CVD apparatus is considered as a superior technique for forming a silicon oxide film and a nitride silicon film as a gate insulating film of a thin film transistor on a large sized glass substrate, an amorphous silicon film such as an active layer and a gate electrode of the thin film transistor on the large sized glass substrate, and a silicon oxide film and a nitride silicon film as an interlayer insulating film of a transistor device on a large sized silicon substrate.
As mentioned above, the neutral gas injection holes 109 are provided near the radical passage holes 105 and the neutral gas is uniformly supplied on the surface from the neutral gas injection holes 109. At this time, the plasma confining electrode 108 of a hollow structure is used, as disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 5-21393). The plasma confining electrode 108 of the hollow structure is provided with the radical passage holes 105 and the neutral gas passage holes 109 independently, as shown in FIGS. 2 and 3. The radicals 104 and the neutral gas 110 are never mixed in the hollow structure.
As a method of supplying the neutral gas from the outside of a vacuum chamber 107 to the plasma confining electrode 108 of the hollow structure, various methods are considered. In a first method, the neutral gas 110 is supplied from an upper direction into the plasma confining electrode 108 through the plasma region 106 by neutral gas introduction pipes 112 as shown in FIG. 4. Also, in a second method, the neutral gas 110 is supplied from a lateral direction into the plasma confining electrode 108 as shown in FIG. 5. The method disclosed in the above-mentioned Japanese Laid Open Patent Application (JP-A-Heisei 5-21393) is of the latter.
In the first method shown in FIG. 4, the neutral gas 110 can be uniformly injected on the surface of the substrate, if a lot of neutral gas introduction pipes 112 are uniformly provided for the plasma confining electrode 108. In this case, however, the neutral gas introduction pipes 112 pass through the plasma generation region 106. As a result, abnormal discharge 117 is generated easily near the neutral gas introduction pipe on the whole of the plasma confining electrode 108, so that the plasma generating state becomes unstable.
Also, in the second method shown in FIG. 5, most of the gas is injected from the neutral gas injection holes near the connection section of the neutral gas introduction pipe 112 with the plasma confining electrode 108. As a result, because the pressure in the plasma confining electrode 108 of the hollow structure is as low pressure as tens to hundreds mtorr which is equal to a film forming pressure in the substrate processing region, the uniform gas injection on the surface is difficult, as schematically shown in FIG. 6.
To solve the above problem, it would be necessary to arrange such a gas diffusing plate as used in a gas shower head of the conventional parallel plate plasma CVD apparatus, in the inside of the plasma confining electrode 108 of the hollow structure. As shown in FIG. 7, the conventional gas shower head structure is composed of neutral gas introduction pipes 112, a diffusing plate 114 having a plurality of holes uniformly provided on the surface thereof and a gas injection plate 115 having gas injection holes uniformly on the surface thereof. In the conventional parallel plate plasma CVD apparatus, a large number of gas supply pipes can be connected to the gas shower head. Therefore, uniform gas injection is possible even in the structure as shown in FIG. 7. In this case, however, it is impossible to supply a gas to the gas shower head while avoiding the above-mentioned abnormal discharge in the remote plasma CVD apparatus. Also, it is difficult to uniformly inject the neutral gas on the surface of the substrate 103 in the method of using the gas diffusing plate as shown in FIG. 7.
In conjunction with the above description, a plasma CVD apparatus is disclosed in Japanese Laid Open Utility Model Application (JU-A-Heisei 1-86227). In this reference, the plasma CVD apparatus is composed of a box electrode, and a counter electrode. A substrate is provided between the electrodes. The box electrode has a fixed intermediate diffusing plate and a movable intermediate diffusing plate. The diffusing plates have a plurality of holes. By adjusting the position of the movable intermediate diffusing plate, the number of gas passable holes and the area of the gas passage hole are adjusted.
Also, a plasma CVD apparatus disclosed in Japanese Laid Open Utility Model Application (JU-A-Heisei 7-27149). In this reference, the plasma CVD apparatus is composed of an electrode section (2) having electrode plates (3 and 4) parallel to a wafer W and a gas introduction pipe (5). A gas G is introduced through the gas introduction pipe (5), passes through the electrode plates (3 and 4), and is supplied to the wafer W. A gas diffusing pipe (10a) is provided in parallel to the electrode plates (3 and 4) to have holes (11) in a radial direction from the gas introduction pipe (5). The gas diffusing pipe (10a) is connected to the connection end (5a) of the gas introduction pipe (5) and has the closed end.
Therefore, an object of the present invention is to provide a plasma CVD apparatus in which it is possible to uniformly inject a neutral gas on a substrate surface.
Another object of the present invention is to provide a plasma CVD apparatus in which abnormal discharge does not occur, even if a neutral gas introduction pipe is inserted into a plasma generation region.
In order to achieve an aspect of the present invention, a plasma CVD apparatus includes first and second electrodes, neutral gas introduction pipes, and a plasma confining electrode interposed between the first and second electrodes to separate a plasma generation region and a substrate processing region. The plasma confining electrode has a hollow structure defined by an upper electrode plate, and a lower electrode plate, and has gas diffusing plates provided in the hollow structure, and has radical passage holes provided to supply radicals from the plasma generation region into the substrate processing region while isolating from a neutral gas. The plasma confining electrode is connected to the neutral gas introduction pipes, and a plurality of neutral gas passage holes are provided for each of the lower electrode plate and the gas diffusing plates to supply the neutral gas into the substrate processing region. A total opening area of the plurality of neutral gas passage holes in the gas diffusing plate on a side of the upper electrode plate is smaller than that of the plurality of neutral gas passage holes in the gas diffusing plate on a side of the lower electrode plate.
Here, the number of the neutral gas passage holes in the gas diffusing plate on the side of the lower electrode plate may be more than the number of the neutral gas passage holes in the gas diffusing plate on the side of the upper electrode plate.
Also, first ones of the plurality of neutral gas passage holes in each of the gas diffusing plates may be different in diameter from second ones of the plurality of neutral gas passage holes in each of the gas diffusing plates.
Also, positions of the neutral gas passage holes in the gas diffusing plate nearer to the lower electrode plate may be different from positions of the neutral gas passage holes in the gas diffusing plate nearer to the upper electrode plate.
Also, a region of the neutral gas passage holes in the gas diffusing plate nearer to the lower electrode plate may be arranged in an outside region of a region of the neutral gas passage holes in the gas diffusing plate nearer to the upper electrode plate.
Also, the gas introduction pipes may extend from a lateral direction of the plasma confining electrode to be coupled to side portions of the plasma confining electrode. Instead, the gas introduction pipes may extend to pass through a peripheral portion of the plasma generation region to be coupled to upper portions of the plasma confining electrode.
In order to achieve another aspect of the present invention, a plasma CVD apparatus includes first and second electrodes, neutral gas introduction pipes, and a plasma confining electrode interposed between the first and second electrodes to separate a plasma generation region and a substrate processing region. The plasma confining electrode has a hollow structure defined by an upper electrode plate, and a lower electrode plate, and has gas diffusing plates provided in the hollow structure, and has radical passage holes provided to supply radicals from the plasma generation region into the substrate processing region while isolating from a neutral gas. The plasma confining electrode is connected to the neutral gas introduction pipes, and a plurality of neutral gas passage holes are provided for each of the lower electrode plate and the gas diffusing plates to supply the neutral gas into the substrate processing region. A distribution density of opening area consisting of the plurality of neutral gas passage holes is higher in a central portion of each of the gas diffusing plates than in a peripheral portion thereof.
Here, the number of the neutral gas passage holes in the gas diffusing plate on the side of the lower electrode plate may be more than the number of the neutral gas passage holes in the gas diffusing plate on the side of the upper electrode plate.
Also, first ones of the plurality of neutral gas passage holes in each of the gas diffusing plates may be different in diameter from second ones of the plurality of neutral gas passage holes in each of the gas diffusing plates.
Also, positions of the neutral gas passage holes in the gas diffusing plate nearer to the lower electrode plate may be different from positions of the neutral gas passage holes in the gas diffusing plate nearer to the upper electrode plate.
Also, a region of the neutral gas passage holes in the gas diffusing plate nearer to the lower electrode plate may be arranged in an outside region of a region of the neutral gas passage holes in the gas diffusing plate nearer to the upper electrode plate.
Also, the gas introduction pipes may extend from a lateral direction of the plasma confining electrode to be coupled to side portions of the plasma confining electrode. Instead, the gas introduction pipes may extend to pass through a peripheral portion of the plasma generation region to be coupled to upper portions of the plasma confining electrode.
In order to achieve still another aspect of the present invention, a plasma CVD apparatus includes first and second electrodes, neutral gas introduction pipes, a plasma confining electrode interposed between the first and second electrodes to separate a plasma generation region, and a gas supply section interposed between the plasma confining electrode and the second electrode to supply neutral gas. The gas supply section has a hollow structure defined by an upper plate and a lower plate, and has gas diffusing plates provided in the hollow structure, and has radical passage holes provided to supply radicals while isolating from a neutral gas. The gas supply section is connected to the neutral gas introduction pipes, and a plurality of neutral gas passage holes are provided for each of the lower plate and the gas diffusing plates to supply the neutral gas into the substrate processing region. A total opening area of the plurality of neutral gas passage holes in the gas diffusing plate on a side of the upper plate is smaller than that of the plurality of neutral gas passage holes in the gas diffusing plate on a side of the lower plate.
Here, the number of the neutral gas passage holes in the gas diffusing plate on the side of the lower gas supply section plate may be more than the number of the neutral gas passage holes in the gas diffusing plate on the side of the upper gas supply section plate.
Also, first ones of the plurality of neutral gas passage holes in each of the gas diffusing plates may be different in diameter from second ones of the plurality of neutral gas passage holes in each of the gas diffusing plates.
Also, positions of the neutral gas passage holes in the gas diffusing plate nearer to the lower gas supply section plate may be different from positions of the neutral gas passage holes in the gas diffusing plate nearer to the upper gas supply section plate.
Also, a region of the neutral gas passage holes in the gas diffusing plate nearer to the lower gas supply section plate may be arranged in an outside region of a region of the neutral gas passage holes in the gas diffusing plate nearer to the upper gas supply section plate.
Also, the gas introduction pipes may extend from a lateral direction of the gas supply section to be coupled to side portions of the gas supply section.
Also, the gas introduction pipes may extend to pass through a peripheral portion of the plasma generation region to be coupled to upper portions of the gas supply section.
In order to achieve yet still another aspect of the present invention, a plasma CVD apparatus includes first and second electrodes, neutral gas introduction pipes, a plasma confining electrode interposed between the first and second electrodes to separate a plasma generation region, and a gas supply section interposed between the plasma confining electrode and the second electrode to supply neutral gas. The gas supply section has a hollow structure defined by an upper plate and a lower plate, and has gas diffusing plates provided in the hollow structure, and has radical passage holes while isolating from a neutral gas. The gas supply section is connected to the neutral gas introduction pipes, and a plurality of neutral gas passage holes are provided for each of the lower plate and the gas diffusing plates to supply the neutral gas into the substrate processing region. A distribution density of opening area consisting of the plurality of neutral gas passage holes is higher in a central portion of each of the gas diffusing plates than in a peripheral portion thereof.
Here, the number of the neutral gas passage holes in the gas diffusing plate on the side of the lower electrode plate may be more than the number of the neutral gas passage holes in the gas diffusing plate on the side of the upper electrode plate.
Also, first ones of the plurality of neutral gas passage holes in each of the gas diffusing plates may be different in diameter from second ones of the plurality of neutral gas passage holes in each of the gas diffusing plates.
Also, positions of the neutral gas passage holes in the gas diffusing plate nearer to the lower gas supply section plate are different from positions of the neutral gas passage holes in the gas diffusing plate nearer to the upper gas supply section plate.
Also, a region of the neutral gas passage holes in the gas diffusing plate nearer to the lower gas supply section plate is arranged in an outside region of a region of the neutral gas passage holes in the gas diffusing plate nearer to the upper gas supply section plate.
Also, the gas introduction pipes may extend from a lateral direction of the plasma confining electrode to be coupled to side portions of the gas supply section.